I. Field of the Invention
The present invention relates generally to nonsurgical procedures and devices and, more particularly, to a method and a minimally invasive infusion/suction catheter system for removing collected epidural fluid related to epidural abscesses and other etiologies surrounding the spinal cord to treat infection and relieve external compression.
II. Related Art
In humans, the vertebral column is a column usually consisting of 33 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsal aspect of the torso. The vertebral canal follows the different curves of the column, it is large and triangular in those parts of the column which enjoy the greatest freedom of movement, such as the cervical and lumbar regions; and is small and rounded in the thoracic region, where motion is more limited. The spinal cord is located inside the vertebral canal and extends from the foramen magnum down to the level of the first and second lumbar vertebrae (at birth, down to second and third lumbar vertebrae). The spinal cord is composed of 31 segments: 8 cervical (C), 12 thoracic (T), 5 lumbar (L), 5 sacral (S), and 1 coccygeal (Co), mainly vestigial. The spinal nerves comprise the sensory nerve roots, which enter the spinal cord at each level, and the motor roots, which emerge from the cord at each level which is formed by the foramina of the 7 cervical, 12 thoracic, 5 lumbar and 5 sacral vertebrae, which together form the spine. The conus medullaris is the cone-shaped termination of the caudal cord. The pia mater continues caudally as the filum terminale through the dural sac and attaches to the coccyx.
Within the vertebral canal, both spinal cord (CNS) and spinal roots (PNS) are enveloped by the meninges. Spinal dura mater is separated from the periosteum lining the vertebral canal by an extradural space that contains a variable amount of fat (in the cranial cavity, dura mater and periosteum merge so an extradural space does not exist). Three layers of meninges envelop the spinal cord and the roots of spinal nerves. The most superficial menix is dura mater. It is protective by virtue of its high collagen content. The space between spinal dura mater and periosteum lining the vertebral bone canal is called extradural space. The dura mater is expansile so the space can accommodate structures with diameter up to 0.06 to 0.07 inches. Arachnoid (arachnoid membrane) is thin and delicate, being composed of flattened fibrocytes and flimsy strands of collagen. In life, arachnoid contacts dura mater due to cerebrospinal fluid pressure within the subarachnoid space. Arachnoid trabeculae are delicate strands of arachnoid that traverse the subarachnoid space to join pia mater. Bilaterally, pia mater collagen is thickened to form denticulate ligaments. Processes of the ligaments periodically join dura mater and thus, within dura mater, the spinal cord is suspended by bilateral denticulate ligaments and thereby surrounded by protective cerebrospinal fluid within the subarachnoid space.
An epidural abscess is a localized collection of purulent material in the extradural space due to bacterial infection causing back pain, spinal cord compression, and systemic manifestations of infection (fever, leukocytosis). Spinal cord compression develops when the spinal cord is compressed by the abscess or other fluid collection. This condition is regarded as a medical emergency independent of its cause, and requires swift diagnosis and treatment to prevent long-term disability due to irreversible spinal cord injury. The present surgical procedure involves exposure of the extradural space to aspirate purulent material to relieve pressure on the spinal cord or the nerve roots. However, the process is extensive particularly when the epidural abscess involves multiple spinal segments and is associated with complications such as destabilization of vertebral bodies and lamina, or worsening of neurological deficits. Furthermore, open surgical removal may result in spread of infection along the surgical tract.
External compression of spinal cord by fluid collection in the extradural space most commonly due to epidural abscess remains a major cause of myelopathy. The external compression of the spinal cord leads to paraparesis, segmental sensory loss and urinary and fecal incontinence. As indicated above, an open surgical approach to alleviate the condition also has the undesirable risk of disseminating the infection in the surgical tract. If an open surgical approach is used, an epidural abscess that spreads over several spinal levels requires a large surgical exposure under general anesthesia. Because of this, a less risky, less invasive procedure has been sought to treat this type of condition.
In accordance with attempts at less invasive methods, epidural catheter devices have been developed including devices that may be able to inject and remove material by combining coaxial inner infusion and outer removal catheters such as shown in Amaki et al. (U.S. Pat. No. 4,737,146). However, that device has certain drawbacks, including an open distal infusion tip and inability to have the inner (infusion) catheter advanced beyond the outer catheter. Thus, it is difficult to maneuver and hard to separate infused material and material to be removed. A dual lumen spinal device is shown in Pub. U.S. Application 2006/0184098 A1 to Barnitz et al. and a dual lumen composite probe device is shown in U.S. Pat. No. 5,447,494 to Dorsey, III. Thus, while a variety of composite suction and irrigation probe and catheter devices have been proposed that are capable of invading the extradural space, there remains a need for a minimally invasive procedure using a more highly maneuverable and adjustable catheter system using various trajectories of flow between infusion and aspiration to more efficiently approach and remove epidural fluid collection related to epidural abscesses and other etiologies surrounding the spinal cord which are located in various compartments to treat infection and internal compression.